What are the causes of delirium in geriatric patients?

Causes of Delirium in Geriatric Patients

The most common causes of delirium in geriatric patients include infections (particularly urinary tract infections and pneumonia), medications (especially anticholinergics and benzodiazepines), metabolic disturbances, and acute neurological conditions. 1

Primary Causes of Delirium

Infections

• Urinary tract infections and pneumonia are the most frequently encountered infectious causes of delirium in older adults 1
• Meningitis and encephalitis, though less common, can present primarily with delirium 1

Medications

• Anticholinergic medications are among the highest-risk medications for causing delirium 1
• Benzodiazepines and other sedative-hypnotics significantly increase delirium risk 1
• Meperidine (Demerol) has particularly high delirium risk compared to other opioids 1
• Diphenhydramine and other first-generation antihistamines with strong anticholinergic properties 1
• Histamine-2 receptor antagonists (e.g., cimetidine) 1
• Polypharmacy (five or more medications) independently increases delirium risk 1

Neurological Conditions

• Cerebrovascular disease, including stroke and transient ischemic attacks 1
• Intracranial hemorrhage (subarachnoid, subdural, or intracerebral) 1
• Status epilepticus and nonconvulsive seizures 1
• Increased intracranial pressure from any cause 1
• Hydrocephalus 1

Metabolic and Endocrine Disturbances

• Electrolyte abnormalities, particularly sodium, calcium, and glucose imbalances 1
• Dehydration and fluid/electrolyte disturbances 1
• Hypoxia and poor oxygen delivery 1
• Acid-base disturbances 2
• Thyroid dysfunction (both hyper- and hypothyroidism) 2
• Hepatic or renal dysfunction 2

Substance-Related Causes

• Alcohol or sedative-hypnotic withdrawal 1, 3
• Drug intoxication 3
• Substance abuse 1

Contributing Factors

Physiological Factors

• Advanced age itself is a significant risk factor due to decreased physiological reserve 2, 4
• Pre-existing cognitive impairment or dementia 1, 2
• Sensory impairments (hearing and vision deficits) 1
• History of stroke 1
• Nursing home residence 1

Environmental Factors

• Sleep deprivation 1, 5
• Physical restraints 1
• Unfamiliar environment 1
• Inadequate pain control 1, 6

Diagnostic Approach

Key Clinical Assessment

• Determine onset and course (acute onset and fluctuating course are hallmarks of delirium) 1
• Assess attention and consciousness (disordered attention and consciousness distinguish delirium from dementia) 1
• Evaluate for presence of hallucinations (often present in delirium but not typically in uncomplicated dementia) 1
• Use validated screening tools such as the Confusion Assessment Method (CAM) or Brief Confusion Assessment Method 1

Essential Investigations

• Complete medication review with special attention to recent changes or additions 1
• Infection workup including urinalysis, urine culture, chest imaging, and blood cultures when appropriate 1
• Metabolic panel to assess electrolytes, renal function, liver function, and glucose 1, 2
• Complete blood count to evaluate for infection or anemia 1
• Oxygen saturation assessment 1
• Consider neuroimaging (CT head without contrast initially) in patients with focal neurologic deficits, history of trauma, or when no other cause is identified 1

Management Principles

Non-Pharmacological Approaches (First-Line)

• Identify and treat underlying causes 1, 3
• Avoid high-risk medications 1
• Provide adequate hydration and nutrition 1
• Ensure proper oxygenation 1
• Use sensory aids (glasses, hearing aids) as appropriate 1
• Maintain regular sleep-wake cycles 1
• Create a calm, well-lit environment with orientation cues 1
• Minimize use of physical restraints 1
• Encourage family presence and familiar objects 1

Pharmacological Management (Reserved for Severe Agitation)

• Antipsychotics at lowest effective dose for shortest duration when non-pharmacological measures fail and patient poses risk to self or others 1
• Haloperidol is preferred over benzodiazepines for acute management of severe agitation 1
• Avoid benzodiazepines except in alcohol or sedative withdrawal 1
• Consider thiamine administration in all delirious patients to prevent Wernicke's encephalopathy, especially with suspected alcohol use 3

Common Pitfalls in Delirium Management

• Failing to recognize hypoactive delirium (quiet, withdrawn presentation) which is often missed but equally serious 4
• Attributing symptoms solely to dementia without investigating for acute causes 1
• Treating symptoms with medications without identifying and addressing underlying causes 5
• Continuing inappropriate medications after resolution of delirium 1
• Overlooking the impact of polypharmacy and not performing medication reconciliation 1
• Inadequate monitoring for medication side effects when pharmacological interventions are necessary 1, 5